Chlorine Demand is the
consistent inability to maintain a chlorine residual in a pool. It is
caused by a build up of contaminants which creates and "overload" on the
sanitizing system. Quite simply, it means that more sanitizer is
required that is being provided to the water.

There are two ways
to treat chlorine demand. The first is to add the appropriate amount of
chlorine. The quickest way to find out what that amount is would be to
have a dealer run a chlorine demand test.
The second way to treat chlorine demand is to drain some of the water
and replace with fresh water. While this will not completely take care
of the demand, it can help lower the amount of product needed.